Thanks, gents.
15mm... I've not tried it, but you're right; I do run my games with a lot of terrain. Shrinking everything down would make it tough for me to get my porky sausage fingers down in amongst 15mm cover and structures.
That said, if you're all set to play ZA/K in a smaller scale, then prepare for those nice, long lanes of fire by kitting out characters with smoke grenades.